move readPixels from bitmap -> pixmap

src/core/SkConfig8888.h

 /*
  * Copyright 2011 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkPixelInfo_DEFINED
 #define SkPixelInfo_DEFINED
 
 #include "SkImageInfo.h"
 
+class SkColorTable;
+
 struct SkPixelInfo {
     SkColorType fColorType;
     SkAlphaType fAlphaType;
     size_t      fRowBytes;
 
     static bool CopyPixels(const SkImageInfo& dstInfo, void* dstPixels, size_t dstRowBytes,
                            const SkImageInfo& srcInfo, const void* srcPixels, size_t srcRowBytes,
                            SkColorTable* srcCTable = NULL);
 };
 
 struct SkDstPixelInfo : SkPixelInfo {
     void* fPixels;
 };
 
 struct SkSrcPixelInfo : SkPixelInfo {
     const void* fPixels;
 
     // Guaranteed to work even if src.fPixels and dst.fPixels are the same
     // (but not if they overlap partially)
     bool convertPixelsTo(SkDstPixelInfo* dst, int width, int height) const;
 };
 
 #endif